Ceratocystis eucalypti sp. nov., a vascular stain fungus from eucalypts in Australia

Abstract

Isolations from stem wounds in living Eucalyptus spp. trees in native forest in eastern Victoria, Australia regularly yielded a Chalara sp. that was morphologically similar to Chalara australis. Unlike Ch. australis, however, sexually compatible isolates were detected, and the teleomorph was formed in culture and also observed occurring on naturally infected wood. A single isolation of the same fungus was also made from a stem wound on E. regnans in Tasmania. The fungus is described as Ceratocystis eucalypti sp. nov. characterized by exceptionally long ascospores which appear to be sheathed. Its anamorph Chalara eucalypti sp. nov., is also described. Mating studies indicate that the fungus is heterothallic with a single locus, bi-allelic mating system. Two mating types were evident among ten field isolates and hermaphrodite and male-only isolates were detected within both mating types. Inoculations of eucalypt seedlings in the greenhouse, saplings in the field and billets cut from cool temperate rainforest species showed that although the fungus can produce a vascular stain, and small cankers in eucalypts, it is only weakly pathogenic.